Identification of novel antisense-mediated exon skipping targets in DYSF for therapeutic treatment of dysferlinopathy

Dysferlinopathy is a progressive myopathy caused by mutations in the dysferlin (DYSF) gene. Dysferlin protein plays a major role in plasma-membrane resealing. Some patients with DYSF deletion mutations exhibit mild symptoms, suggesting some regions of DYSF can be removed without significantly impacting protein function. Antisense-mediated exon-skipping therapy uses synthetic molecules called antisense oligonucleotides to modulate splicing, allowing exons harboring or near genetic mutations to be removed and the open reading frame corrected. Previous studies have focused on DYSF exon 32 skipping as a potential therapeutic approach, based on the association of a mild phenotype with the in-frame deletion of exon 32. To date, no other DYSF exon-skipping targets have been identified, and the relationship between DYSF exon deletion pattern and protein function remains largely uncharacterized. In this study, we utilized a membrane-wounding assay to evaluate the ability of plasmid constructs carrying mutant DYSF, as well as antisense oligonucleotides, to rescue membrane resealing in patient cells. We report that multi-exon skipping of DYSF exons 26–27 and 28–29 rescues plasma-membrane resealing. Successful translation of these findings into the development of clinical antisense drugs would establish new therapeutic approaches that would be applicable to ∼5%–7% (exons 26–27 skipping) and ∼8% (exons 28–29 skipping) of dysferlinopathy patients worldwide. Keywords: exon skipping, antisense, morpholino, dysferlin, dysferlinopathy, limb-girdle muscular dystrophy type 2B, Miyoshi myopathy, distal myopathy, plasma membrane, membrane woundin

Clinical Guides for aHUS

Atypical hemolytic uremic syndrome (aHUS) is a rare disease characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. In 2013, we developed diagnostic criteria to enable early diagnosis and timely initiation of appropriate treatment for aHUS. Recent clinical and molecular findings have resulted in several proposed classifications and definitions of thrombotic microangiopathy and aHUS. Based on recent advances in this field and the emerging international consensus to exclude secondary TMAs from the definition of aHUS, we have redefined aHUS and proposed diagnostic algorithms, differential diagnosis, and therapeutic strategies for aHUS

Quantitative antisense screening and optimization for exon 51 skipping in Duchenne muscular dystrophy

International audienceDuchenne muscular dystrophy (DMD), the most common lethal genetic disorder, is caused by mutations in the dystrophin (DMD) gene. Exon skipping is a therapeutic approach that uses antisense oligonucleotides (AOs) to modulate splicing and restore the reading frame, leading to truncated, yet functional protein expression. In 2016, the US Food and Drug Administration (FDA) conditionally approved the first phosphorodiamidate morpholino oligomer (morpholino)-based AO drug, eteplirsen, developed for DMD exon 51 skipping. Eteplirsen remains controversial with insufficient evidence of its therapeutic effect in patients. We recently developed an in silico tool to design antisense morpholino sequences for exon skipping. Here, we designed morpholino AOs targeting DMD exon 51 using the in silico tool and quantitatively evaluated the effects in immortalized DMD muscle cells in vitro. To our surprise, most of the newly designed morpholinos induced exon 51 skipping more efficiently compared with the eteplirsen sequence. The efficacy of exon 51 skipping and rescue of dystrophin protein expression were increased by up to more than 12-fold and 7-fold, respectively, compared with the eteplirsen sequence. Significant in vivo efficacy of the most effective morpholino, determined in vitro, was confirmed in mice carrying the human DMD gene. These findings underscore the importance of AO sequence optimization for exon skipping